Temperature---Revisited

In two (2) recent studies, determinations were sought as to the effects of temperature on (1) egg development and spawn growth in Koi/Carp (Cyprinus Carpio) and (2) foraging and growth rate of juvenile Koi/Carp (Cyrpinus carpio).

It was shown in the first study that “The present results suggest that water pH 7.5 at water temperature 26°C/79F is best for hatchability of eggs and pH 7.39 for growth of spawn of Cyprinus carpio at same water temperature.

  (Optimal water temperature and pH for development of eggs and growth of spawn of common carp (Cyprinus carpio)

P.H. Sapkalea*, R.K. Singha & A.S. Desaia)

The second study showed “Temperature had a significant and positive effect on the foraging and growth of juvenile common carp Cyprinus carpio (90–105 mm) between 16C/61F and 28C/82F …… These outputs suggest an increase in foraging and growth of C. carpio according to a thermal gradient that were maximal between 24C/75F and 28C/82F.

   (Effects of temperature on the foraging and growth rate of juvenile common carp, Cyprinus carpio   D.O. Oyugi1, J. Cucherousset2, D.J. Baker, J.R. Britton )

Comparing the results of these two (2) studies we quickly see that the temperature of 26C/79F was independently arrived at as the optimal temperature. This temperature is very close, though slightly lower, to what we stated in our previous blog post on temperature in December of 2010.

“Even though no discomfort (stress) is manifested between 20C/68F and 34C/93F, ideally we want the temperature to be close to the midpoint of this range which is 27.5C/81-82F.  This is well above the median temperature recommended by many sources, but is shown to be the ideal temperature for the Carp’s (Koi’s) optimum metabolism.”

Are Pond Ionizers Safe? You be the judge.

Certain manufacturers of Pond equipment decided to borrow a technology from the Swimming Pool industry and, with maybe some minor tweaks, promote it as an exciting breakthrough in controlling Pond algae. Presenting the IONIZER!

Through the controlled release of Copper, Zinc and Silver ions into the pond’s water column, algae growth can be controlled and in many cases eliminated. This, on the surface, is great news for Pondkeepers. No longer is it necessary to use expensive and hard-to-correctly-measure chemicals. Just set the Ionizer to the desired level and algae disappears.

Sounds great! However, there is more to be considered than just what the advertisements claim. What are the other potential and likely results from use of this device that the manufacturers are not telling us?

Let’s look at some of the manufacturers’ claims as regards Ionizers.

Company #1 - “Destroys Bacteria                                 

                              Kills Algae

                              Reduces chemical cost

                              Eliminates chemical odors

                              Reduces maintenance

                              Environmentally Friendly

                              Costs pennies per month

                              Helps reduce filtration

                              Fish safe

                              Includes 2" T Fitting”

Company #2 -     “Safe for fish and plants

                            Low maintenance

                            Clears water without the use of harsh chemicals

                            Easily installed in any new or existing water feature

                            Treats ponds up to 25,000 gallons

                            Level of mineralization is controlled by the LED panel

                            Cast mineral anodes are self-cleaning

                            1 year warranty”

Company #3 –“Drastically reduces pond maintenance

                              Crystal clear water without the use of chemicals

                              Eliminates unsightly water conditions

                              Simple to install

                              Safe for fish and plants

                              Not toxic to animals that may drink from the pond

                              Energy efficient (less than $ 1 a month in electricity cost)

                              Treats ponds up to 25,000 gallons”

Understandably, the first concern of a Pondkeeper is whether a product or treatment is safe for fish. All three (3) of these manufacturers declare that the (proper) use of this device is safe for fish. Let’s take a closer look at this claim.

All Three (3) manufacturers include test strips for monitoring Copper levels with Two (2) of the manufacturers recommending maximum Copper levels at 0.25 mg/L and the remaining manufacturer recommending 0.30 mg/L as the maximum level of Copper.

Copper is a heavy metal and in low concentrations can be toxic. In addition, like other heavy metals, such as Mercury, it is a bio-accumulate. This means that once it is ingested by an organism it remains in that organism for an extended period of time, in many cases, for life. Any additional ingestion only increases the level that is already present in the organism until eventually a certain level of toxicity is reached. For terrestrial organisms, this level is determined primarily by the ingestion of food and water, but for aquatic organisms, if the Copper is in suspension as ions, it may be ingested during the respiration process also, as is the case with fis juvenile amphibians, certain insect larvae, true aquatic invertebrates and bacteria as well as the target taxa of algae. In the case of fish, it causes increased mucous production on the skin and the gills where it eventually interferes with the respiration process by blocking the absorption of Oxygen.

In assessing the potential toxicity of any substance to any organism, two (2) distinct levels must be determined, acute (immediate short term) and chronic (long term). Heavy metals have long been known to play an important beneficial and cricial role in animal and plant physiology, but at levels so low that they are undetectable by standard testing.

Considerably greater attention has been given, in recent years, to the effect of Heavy Metals and other chemical compounds on the environment. Research is ongoing in both the public and private sector. This research has resulted in some universally accepted toxicity levels as regards Heavy Metals.

The focus here will be on Copper. Copper, after Mercury, is the most toxic of the Heavy Metals. Copper’s toxicity is greatly influenced by water Hardness and pH. As water Hardness and ph increase, the toxicity of Copper is reduced. Here is an example of a couple of simple formulae that are used to define the accepted level of Copper in fresh water.

    Maximum Copper levels (in micrograms) at any time—0.094(hardness)+2 (where water Hardness is reported as mg/L  CaCO3.

     30 day average Copper levels (in micrograms)—0.04 average hardness (where water Hardness is reported as mg/L  CaCO3.

       (Environmental Protection Division, Ministry of Environment, Government of British Columbia)

Note - There are other formulas used by different government entities worldwide, but the final accepted levels of Copper vary by only a few micrograms.

Using these two (2) formulae, in water with a Hardness of 120 ppm for example, we find the recommended Copper levels to be 13 micrograms/L at any one time and the 30 day average should not exceed 5 micrograms/L  Knowing that one milligram equals 1000 micrograms, these results expressed in mg/L would be 0.013 mg/L and 0.05 mg/L. These results appear to be on the conservative side, but considering the fact that some aquatic organisms have a very low tolerance to Copper, these formulae are quite appropriate.

These are the Metal Safe Limit levels as defined in the Textbook of Fish Health: Copper 0.014mg/l More toxic in soft water; Zinc exacerbates toxicity; Combined both are dangerous; Zinc 0.01mg/l Synergistic with copper; 0.15mg/l In hard Water; Cadmium 0.03mg/l; Chromium 0.10mg/l; Lead 0.01mg/l In soft Water; 4.00mg/l In hard Water; Silver 0.03mg/l (mg/l is the same as ppm).

The author was unable to find any scientifically set copper toxicity levels for Koi, but several anecdotal sources were found that stated that Koi begin to show copper toxicity at 0.03 ppm along with the copper toxicity level for Koi at 0.3 ppm., which is at or extremely close to the Maximum levels suggested by the manufacturers of these devices. It should be stressed that no scientific studies were found that substantiated these levels. In fact, one study reported that Koi fry were unaffected by Copper levels of 1.00 mg/L.

It is important, however, to know the signs and symptoms of Copper toxicity in Koi. One of the earliest effects of  too much copper is apparent fish hypoxia, the loss of ability to use oxygen. Common symptoms of initial acute toxicity are fish gasping, disoriented (ataxic) at the surface, due to copper's hemolytic (blood cell splitting) and mucus-producing effects. Copper is a proteinaceous precipitant; that is, it causes your fish to produce more mucus. This may aid the in the suffocation or sloughing off of parasites, but also interferes with respiration through their skin and gills.

Of greater concern is the previously mentioned fact that all heavy metals are bio-accumulates. This accumulation leads to immunosuppression.  Fish are often observed suffering from bacterial infections for no apparent reason.   Water quality is optimum but low levels of copper and/or zinc are present. Metals are most toxic in low alkalinity and pH. This allows for a higher concentration of metal to remain dissolved. The accumulation over time immunosuppresses the fish and allows the normal pathogenic bacteria to gain the upper hand leading to ulceration and possible septicemia (bacteria in the bloodstream).

In eco-system ponds, along with the fish, the toxicity of copper to all other aquatic organisms is of equal importance. Considerably more data is available on the effects of copper on fresh water fauna due to the fact that they are present in every natural waterway and their numbers and diversity are prime indicators of the health of any aquatic eco-system.

Copper is extremely toxic to most invertebrates and the juvenile forms of most amphibians.

“Northern leopard frogs (Rana pipiens) were exposed to environmentally relevant concentrations of copper in water (control and 5, 25, and 100 microg/L, as CuSO4) in a static renewal system for 154 d from posthatch stage to metamorphosis. Tadpole survival, swimming performance, percent metamorphosis, time to metamorphosis, and survival during and time required for tail resorption were negatively affected in the 100-microg/L treatment.”

      -Adverse effects of chronic copper exposure in larval northern leopard frogs (Rana pipiens).

Chen TH, Gross JA, Karasov WH.

Available toxicity data on amphibians indicate copper 96 h LC50 values calculated in tadpoles ranged from 0.04 to 5.38 mg/L. Studies of other aquatic organisms show 96 h LC50 values ranging from 0.06 to 6.68 mg/L.

Representative toxicity levels for some other fresh water organisms are-

    Most snails – 8 - 41 micrograms/L; Cladocerans (including Daphnia) 5 - 213 micrograms/L; Amphipods 8 - 87 micrograms/L

Although the Mayfly is fairly sensitive to Copper, the majority of insects that have aquatic larval stages are tolerant, most notable Damselflies and Dragonflies, which are always expected visitors to any aquatic venue. These Odonates have the ability to store heavy metals in their exoskeletons where it remains harmless.

The inhibition, reduction or elimination of any member group of the aquatic food chain will have negative effects on the overall health of the eco-system to a lesser or greater degree depending on which species are residents of that particular eco-system and their relative position in the food web.. Nevertheless, any negative effect on an aquatic eco-system’s food chain and/or diversity will have deleterious effects on the entire system.

The only organisms that have not been discussed are the bacteria, in particular, the nitrifying bacteria. The results of studies on the toxic effects of Copper are quite surprising. Copper and Zinc appear to be the least toxic of the metals tested. Copper, at low levels, actually stimulates activity in  Nitrobacter. At levels up to 0 50 mg/L the Copper ion has no toxic effect on Nitrobacter. Instead, the stimulatory effect is readily apparent......Apparently. at 0 50 mg/L Copper has not reached the cross-over point where a chemical shows neither stimulatory nor inhibitory effects. This, unfortunately, is not true of Nitrosomonas. Growth of Nitrosomonas is greatly inhibited (about 60%) by Copper concentrations of 0.20 ppm. 

      Growth of Nitrosomonas europaea in batch and continuous culture  (Skinner & Walker 1960)
Copper was also found to be one of the most toxic metals to heterotrophic bacteria in aquatic environments.
Sadly, company #1 is partially correct in claiming that their ionizer “destroys bacteria”.

In conclusion, based on the above data, we arrive at these facts-

  -Ionizers can indeed control and, in some instances, eliminate many species of algae.

  -Within the manufacturers’ suggested range of use, 0 – 25/30 mg/L, neither Koi or Goldfish should exhibit any immediate effects of Copper toxicity. It has been shown that Koi fry can tolerate levels of 1.00 mg/L. Due to lack of any meaningful research, long term (chronic) effects are unknown.

  -Copper at low levels is extremely toxic to aquatic stages of most amphibians.

  -Most microorganisms exhibit toxic effects of Copper at extremely low levels and, where mortality does not occur, the effects are compounded in second generations.

  -The effects of relatively low (.20 ppm) Copper levels on one of the main species involved in Nitrogen conversion has the potential to cause major problems in the form of Ammonia spikes.

Considering the whole picture regarding the impact that an Ionizer may have on an aquatic eco-system, this author has no intention of availing himself of its use. There are other effective and absolutely safe ways of controlling and/or eliminating algae. You, the reader, may feel differently. After all, it’s your Pond and your fish.

You be the judge!

_______________

Update Nov. 29, 2012

There has long been a dearth of information regarding the toxicity level of Copper in Koi (Cyprinus carpio). Finally some figures are being established by scientific research.

According to a recent research paper (Dietary tryptophan changes serum stress markers, enzyme activity, and ions concentration of wild common carp Cyprinus carpio exposed to ambient copper

Fish Physiology and Biochemistry (2012) 38: 1419-1426 , October 01, 2012

By  Hoseini, Seyyed Morteza; Hosseini, Seyed Abbas; Soudagar, Mohammad), Carp exposed to 10 mg/L Copper exhibited mortality rates of 21.7 ± 7.6 % at 120 hours and 61.7 ± 10.4 % at 168 hours. Although this level of Copper is 40 times the (claimed) maximum levels generated by ionizers, I feel that it is safe to infer, because Cu is a bio-accumulate, that depending on the usage (level settings and duration of these settings) of ionizers, that Koi/Carp would exhibit physiological and behavioral signs of toxicity much quicker than was originally thought….months instead of years. Hopefully more definitive figures will be forthcoming.

______________

Update July 8, 2014

In this recent research paper - Acute effect of copper exposure on serum biochemical characteristics of common carp (Cyprinus carpio L.), Melika Ghelichpour the effects of low level exposure to Copper were markedly detectable.
"Effects of ambient copper was investigated on serum stress markers, sodium and enzyme levels in Common carp (Cyprinus carpio L.) over a 14-d exposure period. Fish were exposed to 0, 25 and 100 microg L-1 copper (as copper sulfate) and blood was sampled at 0, 3, 7 and 14 d after exposure. Serum profile was significantly affected by copper concentration, sampling time and their interaction. Increase in serum levels of cortisol, glucose, alanine aminotransferase and aspartate aminotransferase and decrease in serum sodium levels were observed in both copper-exposed groups, 3 d after copper exposure, which lasted until the end of the experiment. It is concluded that copper exposure causes stress response and sodium loss in common carp. Likewise alanine aminotransferase and aspartate aminotransferase increase after exposure which might be as results of either tissue damage or stress."
Note: Copper Sulfate readily disassociates in water producing Copper ions. The physiological effects would be the same with an ionizer.




_________________

UPDATE  June 23, 2015

Just released article

“ Health status of two ornamental fishes Poecilia reticulatae (Guppy) and Carassius auratus auratus (Gold fish) following exposure to therapeutic levels of Copper sulphate

M.H.B.W.M.D.N.H. Wickramasinghe* and A. Pathiratne”

…indicates that gill damage occurs in Goldfish at Copper levels of 0.10 mg/L and may not be completely reversible at levels of 0.30 mg/L and recommends that “precautions should be taken especially with the high concentration of CuSO4 (Copper) as it may lead to transient ill health conditions in the exposed fishes.”

When you care enough........

All Water Features support life. We know that any surface that remains wet with water will support, at the least, a microscopic biofilm composed of bacteria, archaea and algae. In decorative Water Features such as formal fountains, water walls and rock bubblers, because of aesthetic considerations, the water is usually treated with chemicals to inhibit the growth of this biofilm.

The opposite is true in Water features that are purposely constructed to support life such as a Water Garden, turtle pond, Garden Pond, etc. This biofilm growth is desired and , indeed, encouraged for it is the foundation of life. It supplies the basic mechanisms in the Nitrogen cycle as well as the Carbon cycle. The greater the surface area of this Biofilm, the more varied and larger organisms that can be supported.. Only when this surface area is large enough can a stable population of fish  be sustained and thrive.. There must be enough biofilm to oxidize the Ammonia and other wastes produced by the fish and support an adequate food chain.

In Nature, this balance is a naturally occurring process. It is when we strive to construct artificial aquatic environments that some outside intervention is usually required by providing supplemental bio-conversion through the use of ‘biological filters’ and by supplemental feeding that may be needed to correct any existing food chain deficiency.

These questions arise:

Do I need ‘bio-filtration’?

If the Water Feature is strictly a Water Garden (No fish, turtles, ducks etc), supplemental bio-conversion is not needed. However, if the Water Feature is to house any of these, then additional bio-conversion is usually a definite requirement. Granted, although a feature of large enough submerged surface area may comfortably support a limited fish population, most people neither have the space or desire to dedicate a few thousand square feet of property to house a handful of fish.

What type and size of ‘bio filter’ do I need?

Type of ‘bio-filter’ is a matter of personal preference…cost, ease of maintenance and possibly aesthetics are possible considerations. Size is of greater importance only as it relates to filter media capacity which itself is dependant on the type of filter media used., the quantity of said media being dependant on its Specific Surface Area (SSA) and primarily on the fish load (biomass) in the Water Feature. (Additional information on SSA and fish load can be found on the internet with a simple web search.)

This brings us to the real purpose of this article; the fact that, in most instances, manufacturers of bio-filtration units supply incomplete and often misleading information on actual filter performance. Some only give the maximum flow rate, many rate their filter on total gallons of pond capacity (Is that without fish? If it is with fish, how many?), still others classify their filters pond capacity with sub classifications of ‘No fish, a few fish, or a heavy fish load”

How many are a “few” and what constitutes “a heavy fish load”. Some give the maximum number of fish in total inches of length which can be dangerously misleading (a 10” fish has considerably more biomass and produces proportionately more waste than two 5” fish of the same specie). One manufacturer does correctly state that it depends on the type of filter media used. Only one manufacturer, that also supplies the media with their filters, gives an actual maximum fish load (in pounds). A koi length/weight calculator is available at http://www.cnykoi.com/calculators/calcnh3c.asp.

Is it surprising then that because of this negligence on the part of the manufacturers new pond owners quickly begin to have problems maintaining water quality? Could this all be due to the fact that they were given incomplete information on the performance abilities of the biological filter they purchased?

Is it truly negligence on the part of the manufacturers? Or carelessness? Or incorrect prioritizing of published technical information? Or is this crucial information withheld knowing that subsequent problems may arise forcing the consumer to purchase yet another piece of equipment or an otherwise avoidable chemical treatment?

It is time that the Water Feature equipment and supply manufacturers adopt industry wide standards concerning labeling and product performance information that would be truly beneficial to the consumer. Knowingly withholding any vital product information seems, at the least, unethical and unprofessional. Some may even feel, and understandably so, that it borders on the criminal.

Before you purchase any filtration unit, ask the important questions and insist on detailed and specific answers. The health and longevity of your fish depend on it. When you care enough….!

...and a cast of thousands!

An excerpt from a movie poster? Could be, but no. I am talking about the multitude of micro-organisms (plant and animal) that call your pond home. I briefly discussed those that live on the bottom or Benthic layer in a previous post. In this post I want to explore those that live in the water column. They are commonly referred to as Plankton.

Plankton is divided into two (2) groups-

   -Phytoplankton which is microscopic plants (algae) and some species of bacteria. These are the primary producers in the aquatic food chain.

   -Zooplankton consists predominately of crustaceans and rotifers. They are usually larger than phytoplankton. They are predators and feed on phytoplankton and other zooplankton.

As an example of the sheer magnitude of their numbers, in a fish culture pond it is not unusual for plankton (dry weight) to account for up to 50% of the total biomass (dry weight) of the pond (this includes the fish). That is a lot of little critters! But very important little critters! They comprise the bulk of any aquatic food chain and web. A pond’s biological balance would collapse without their existence in such great numbers

.

Your Koi and/or Goldfish may be the Stars in your perception but, in biological terms, they are only bit players. They, because they are the top consumer in the food chain, are dispensable as far as maintaining biological balance. The lower an organism exists in the food chain, the more indispensable they become. This truly makes the existence of algae, for instance, more important than the fish. This is not to say that you can’t have too much algae. An overgrowth of algae can be problematic for the balance in a pond as can too many fish.

The USDA recently did away with the Food Pyramid in favor of a dinner plate diagram as a nutritional guide. I prefer the pyramid for it emphasizes the real importance of the food groups. Those most important and also in greatest numbers are at the bottom or base of the pyramid. The same applies to the food chain in a pond. Those organisms of greatest number and importance are at the bottom.  Phyto-plankton.are part of this pyramid base.. Zooplankton are just one level higher in the pyramid.

All plankton serve as nutritional sources for organisms higher in the food chain. Insects, amphibians, annelids and some fish specie look to plankton as a food source.

Just observe all of the activity around your pond. It can be quite a pageant. A pageant that requires........... ‘a cast of thousands’.

Algae - The Propitious PITA

Listen in on most any conversation about ponds and you will eventually hear the word Algae mentioned, many times along with some unpleasant descriptive adjectives. In the majority of cases, it is the ‘Green Algae’ that is the subject of the verbal derision.

It is true that out-of-control algae can turn an otherwise beautiful Water Feature into a most disgusting eyesore. It is wrong, however, to put any blame on this simple organism. “Don’t shoot the messenger”.  Algae are not the problem. It has been explained in countless means of communication, for countless times and for countless years that….excess algae is a direct result of an excess nutrient level in the pond water. So, if your pond has an abundance of algae, it is your fault because: (a)You have too many fish; (b) You overfeed your fish; (c) You do not have a sufficient size aquatic plant population; (d) You allow leaves, twigs and other organic debris to accumulate in you pond; (e) All of the above.

Algae are, by their nature, quite beneficial. Nearly all algae are photosynthetic (the ability to produce Oxygen), so much so that the total amount of Oxygen produced by all algae EXCEEDS the total amount produced by the entire plant kingdom. That’s impressive!

Algae are an extremely important source of nutrition for most aquatic organisms and are an integral part of the foundation of the overall food web. Extremely high in nutritional value, several species of Algae are used for human consumption, from wrapping sushi (Nori-Red Algae) to nutritional supplements such as Chlorella and Spirulina (Green Algae).

There are over 300,000 identified species of algae (no one knows the exact number) and around 6,000-7,000 species of green algae (again no one know for sure) and range in size from the single cell microscopic to the multi-cell giant sea kelp

Algae have existed in vast numbers for millions of years. The sparkling white sand beaches of the Caribbean and many other areas in the world are largely the sun-bleached and eroded calcium-carbonate remains of green algae.

They are an important part of the Nitrogen cycle (the use of Nitrates as an energy source) and the Carbon cycle. Like Oxygen, the total amount of Carbon contained in all algae exceeds the total amount contained in the entire plant kingdom.

In conclusion, the next time you think of hurling epithets at the green invasion of your pond, just remember all of the beneficial aspects of algae and, more to the point, remember that it is likely your fault. Like any other pesky organism…quit feeding it and it will go away.

Archaea: The not-so-new kids on the block

The oxidation of Ammonia was for decades believed to be performed solely by certain autotrophic bacteria (i.e. Nitrosomona)  Later it was discovered that this oxidation process was also performed by certain Heterotrophic bacteria under certain conditions that were completely void of any organic carbon source or oxygen.

With the advent of gene sequencing, it was discovered in 1977 that what was thought to be a type of bacteria was actually not a bacteria at all, but an entirely different and new domain. This group of microorganisms was given the name “Archaea”.

Originally thought to be exclusively extremeophiles that lived in environments such as hot springs and very acid and saline conditions, it was recently (2006) discovered and subsequently verified (2008) that Archaea are ubiquitous and exist in all environments and more importantly play a very large role in the oxidation of Ammonia. Unlike nitrifying bacteria, nitrifying Archaea are suspected to be adaptable to a wider range of temperatures. Evidence of their existence has been found in the very cold waters of Antarctica.

Unfortunately, at the present time, Archaea are very difficult, if not impossible, to reproduce under laboratory conditions, so current knowledge is limited.

No nitrite oxidizing Archaea have been detected to date, but, given the relative infancy and current limits of research, this does not mean that they don’t exist.

The results of future research could have a major impact on how we view the basic biological processes of our ponds. For example, it has already been shown that Archaea tend to colonize the rhizosphere (root zone) of aquatic plants. This fact alone increases the importance of aquatic plantings in maintaining water quality. Archaea’s wider tolerance of extreme temperatures could possibly shed light on why some Northern ponds endure winter stresses better than others.

Much still needs to be learned about this newly named, but very old, microorganism.

The Benthos

"The length of food chains is a crucial determinate of the functioning of ecosystems," says Alan Tessier, program director in the National Science Foundation (NSF)'s Division of Environmental Biology.

Roughly translated, diversity in an eco-system is of prime importance. This diversity is not limited to the number of levels in a food chain, but the diversity within each level provides a key element of stability to the entire food chain. The lower the level of the food chain, the more important and crucial this diversity becomes.

Biofilm, as indicated in the previous post, forms the true foundation upon which an aquatic food chain is established. Also of extreme importance is what is called the Benthic layer or Benthic zone.

The Benthic zone is the ecological region at the lowest level of a body of water including the sediment surface and some sub-surface layers. This region extends from water’s edge to water’s edge and encompasses the shallow (littoral) regions as well as the deepest (i.e. the profundal region that exists is lakes).Organisms living in this zone are called Benthos. They generally live in close relationship with the substrate bottom; many such organisms are permanently attached to the bottom. The superficial layer of the soil lining the given body of water, the benthic boundary layer or BBL, is an integral part of the benthic zone, as it influences greatly the biological activity which takes place there.

Benthos, in fresh water biology, refers to organisms at the bottom of bodies of water, such as lakes, ponds, rivers, and streams. The population make up of these communities is influenced not only by type of body of water, but also by the depth of the water plus nutrient availability and, of course, pH and temperature.

There are two types of Benthic organisms:

          Epifauna- live on the surface of the bottom

            Infauna- burrow into the sediment on the bottom

Of the two, Epifauna is the most prevalent form found in an eco-system pond, although some Infauna may exist depending on depth of bottom gravel and the amount of sedimentation.

They are also classified as to size:

Microbenthos (<100mm) includes bacteria & protests

Meiobenthos (100-500mm) includes small metazoan (multicellular animals) and larger protists (single cell organisms).

Macrobenthos (>500mm) includes larger metazoa and Megabenthos

          Megabenthos (very large.)  crustaceans, mollusks, etc.

By what they eat:

Herbivores- feeds on plant material

Carnivores/predators- feeds on other benthic organisms

Detritivores- feeds on dead plant and animal material

And how they eat:

Suspension feeders- eats using a mucus-covered appendage that catches particles in water column

Filter feeders- strain particles from the water column

Deposit feeders- ingest sediment and removing the nutrients

In our next post, we will delve deeper into the roles that each individual type plays in the complex world of an aquatic eco-system. It will be the beginning of an interesting journey into a world of such immense activity that, by comparison, the activity level of your fish is like watching paint dry.

Periphyton Part 1 - Biofilm

Periphyton

Introduction

It is usually green. It is almost always slimy. It is seldom attractive. It is universally cursed and derided by many Pond Keepers. It is, however, the most important grouping of organisms in any aquatic eco-system. It is generally called Periphyton.

Although the dictionary defines Periphyton as “aquatic organisms, such as certain algae, that live attached to rocks or other surfaces.”, there are a bevy of terms that refer to the particulate organic matter (POM) attached to rocks and other submerged surfaces: “aufwuchs”, “biofilm”, “benthic algae”, the epi-s: (epilithon [rock], epipelon [mud], epissamon [sand], epixylon and epidendric [wood],  epiphyton [plants] and epizoic [animals, such as snails and Caddis fly larvae] ) and, of course,  “periphyton”. 

The use of the term Periphyton by the scientific community usually encompasses two communities of microorganisms-

    Biofilm- microbial communities, predominantly bacteria, encased in a layer of extracellular polymeric substances (EPS).         

    Aufwuchs (pronounce: OWF-vooks, German, "growth upon")  the fuzzy, sort of furry-looking, slimy green coating that attaches or clings to stems and leaves of rooted plants or other objects projecting above the bottom without penetrating the surface. Unlike Periphyton, it includes not only algae like Chlorophyta, but also diatoms, nematodes, protozoans, bacteria, fungi and myriad other tiny creatures such as Tardigrades.

It is only through the examination of these two (2) groups of organisms both in internal structure and function and the interrelations within and among these two (2) groups can we truly understand the importance of these groups to overall water quality.

Part 1

Biofilm

Biofilm is the foundational structure of these combined communities and may vary in thickness from only a few micrometers to several hundred micrometers, from the thickness of a single cell to multiple layers and community groupings.

Biofilm-  “A complex structure adhering to surfaces that are regularly in contact with water, consisting of colonies of bacteria and usually other microorganisms such as yeasts, fungi, and protozoa that secrete a mucilaginous protective coating in which they are encased. Biofilms can form on solid or liquid surfaces as well as on soft tissue in living organisms, and are typically resistant to conventional methods of disinfection. Dental plaque, the slimy coating that fouls pipes and tanks, and algal mats on bodies of water are examples of biofilms. While biofilms are generally pathogenic in the body, causing such diseases as cystic fibrosis and otitis media, they can be used beneficially in treating sewage, industrial waste, and contaminated soil.”  (The American Heritage® Science Dictionary)

Biofilms are a crucial part of an aquatic eco-system. The microorganisms that make up biofilms form the basis for food webs that nourish larger organisms such as insect larvae, which are consumed by fish. Even plants benefit from naturally occurring biofilms.

The instant that the first water contacts any surface of your pond, whether it be liner, rock, filter media, plants etc., biofilm begins to form. Initially the first surface deposits are TEPs (transparent exopolymer particles) planktonic organic microgels that are ubiquitous in aqueous environments, which neutralize the electrical charge of the surface which would otherwise repel bacteria and other microorganisms. This initial layer of organics also serves as a nutrient source. Bacteria then begin to colonize the surface by secreting strands of sticky polymers (extracellular polymeric substances or EPS) which holds the biofilm together in a structural matrix and secures it to the surface. These polymers also serve to trap nutrients and act as very strong protective barrier against toxins.

As nutrients accumulate, the original bacteria multiply. These offspring bacteria produce their own sticky polymer. Soon a colony of bacteria is established.  

 These “other bacteria and fungi become associated with the surface following colonization by the pioneering species over a matter of days.” Borenstein (1994),

(Whal, 1989) discussed the settling pattern of biofilm in four phases: (i) surface conditioning or adsorption of dissolved organic compounds where macromolecules attach to submerged surfaces following a spontaneous physical-chemical process; (ii) primary colonization or bacterial settling following surface conditioning and after their colonization, bacteria start to produce EPS, (iii) secondary colonization to bacterial layer and EPS pool by eukaryotic unicellular microorganisms, mainly protozoan, microalgae and cyanobacteria and (iv) settling of eukaryotic multicellular organisms as a function of nutrient sharing, grazing and predation. According to (Wetzel, 1983), associated organization from secondary colonization onwards can be designated as “periphyton‟. In that way, it could be defined as an advanced successional stage of biofilm. However, there could be a fifth (v) phase; the tertiary colonization where bacterioplankton colonized on the surfaces of unicellular and filamentous secondary colonizers (e.g. diatom, Oedogonium etc.).

Once a certain bacterial population level is reached, a process called ‘quorum sensing’ occurs. Quorum sensing is a cell-to-cell communication through the use of chemical autoinducers that allows populations of bacteria to simultaneously regulate gene expression in response to changes in cell density.

Biofilm is made up of microorganisms and a polymeric web. Interestingly, in a well established biofilm, most of the volume is the sticky polymer matrix (75%-95%). This matrix holds quite a bit of water and makes the biofilm covered surface slippery. This is why, especially in bare liner ponds, it is difficult to maintain traction while you are wading in your pond.

A fully developed biofilm is a complex mutually beneficial community of various microorganisms living in a customized microniche.

 “Different species live cheek-by-jowl in slime cities, helping each other

to exploit food supplies and to resist antibiotics through neighborly

interactions. Toxic waste produced by one species might be hungrily

devoured by its neighbor. And by pooling their biochemical resources

to build a communal slime city, several species of bacteria, each

armed with different enzymes, can break down food supplies that no

single species could digest alone. The biofilms are permeated at all

levels by a network of channels through which water, bacterial

garbage, nutrients, enzymes, metabolites and oxygen travel to and fro.

Gradients of chemicals and ions between microzones provide the

  power to shunt the substances around the biofilm.” Slime City (Coghlan 1996)

A mature biofilm may take several hours to several weeks to develop. A fully developed biofilm is able to move water through the entire matrix, supplying nutrients and transporting wastes. Biofilms may be very thin to several inches thick. The biofilms that are usually encountered in an aquatic eco-system are measured in microinches. A microinch is equal to one-millionth of an inch. The congregation of multiple species into biofilm microcosms increases the range of organic and inorganic substances that can be biodegraded

In aquatic systems the biofilm bacterial count per square centimeter of surface has been estimated to be approx 1000-fold higher than the corresponding planktonic count per cubic centimeter

Biofilm covers every submerged and constantly wet surface associated with a pond. It is on the rock, liner, plants, skimmer, biofilter and media, even inside of the pump and related piping. The biofilm in one location will be different in make up than that in another location. Factors such as light, water movement, temperature and availability of nutrients will determine the member microorganisms of each community. The very same parameters that we test for to ensure healthy fish also influence the membership of the biofilm community.

It is within this biofilm that nitrification and denitrification take place along with other chemical and organic conversion processes.  

Biofilm is the primary source of production in an aquatic system. It is what sustains all higher levels of aquatic life.

Updated- Feb. 23, 2014

Are Koi Wusses? Part IX - Denitrification

Denitrification is the bacterial process where Nitrate is reduced to gaseous Nitrogen. This is accomplished in a series or steps: Nitrate to Nitrite, Nitric oxide, Nitrous oxide and finally Nitrogen gas.

Denitrification is accomplished by primarily Heterotrophic and Autotrophic bacteria, with Heterotrophic bacteria playing the larger role. Autotrophic bacteria utilize sunlight and inorganic chemicals as an energy source, whereas Heterotrophic bacteria rely mainly on organic carbon as an energy source.

Denitrification takes place under special conditions in both terrestrial and aquatic ecosystems. It occurs where Oxygen is depleted, and bacteria utilize nitrate in the respiration process. Due to the high concentration of oxygen in our atmosphere, denitrification only takes place in environments where oxygen consumption exceeds the rate of oxygen supply, such as in some soils and groundwater, wetlands and the substrates in the bottom of a pond.

In a properly constructed eco-system pond, denitrification is a normally occurring process. A classic Koi pond, however, because of its method of construction (no rock or gravel; bare liner), does not have any areas of low or depleted Oxygen to promote the growth of these denitrifying bacteria. External methods must be used for denitrification such as trickle towers, fluidized beds and rotating biological contactors. Additionally, attention should also be given to ORP (oxidation reduction potential) levels.

In the previous post, the toxic level of Nitrate was shown to be arbitrary at best. This was focused on high end Nitrate levels. The complete absence of Nitrate (in an eco-system pond), however, is definitely cause for concern. In the absence of Nitrate, the denitrifying bacteria will utilize Sulfur as a replacement, producing Hydrogen sulfide (rotten egg gas) which is highly poisonous. It should be pointed out that, for this scenario to occur, the pond would have to be completely neglected……a total lack of maintenance or ownership responsibility or concern.

This, then, is where the Nitrogen cycle comes full circle. With very few exceptions, all living organisms rely on this continuous process for their existence.

The subject may be debated for years to come, but it has been shown that Carp (Koi) are some of the most durable and adaptable fish in existence. I think that the Australians have summed up the hardiness in Carp (Koi) by referring to them (not very affectionately) as “River Rabbits”.

We can now begin venturing into the world of aquatic life; exploring the succeeding higher levels of the Food Web and how they interact.

Are Koi Wusses? Part VIII - Nitrate

Nitrate is the product of  the oxidation of Nitrite by, primarily, the bacteria genus Nitrobacter, and, to a lesser extent, the genus Nitrospira.

It is generally believed that Nitrate is toxic to Carp (Koi) only at very high levels. There is much disagreement as to at what level does Nitrate begin to have toxic effects. This is primarily due to the lack of research done on this subject as relates to Carp (Koi). Some believe that most fish easily tolerate levels below 100 mg/L; others claim that levels above 120 mg/L are toxic; still others state that fish can tolerate levels up to 500 mg/L.

The important aspect of Nitrate toxicity to remember is that it is species specific. Scientific research has shown that Nitrate levels of 10 mg/L, which is the maximum safe level for drinking water, IS toxic, at least in the long term, to certain sensitive freshwater invertebrates, fish and amphibians.

The toxicity level in an eco-system pond is, for all practical purposes, a non-issue.

Aquatic plants utilize Nitrate as a food source. If excessive Nitrate occurs, Nature has a built in balancer…ALGAE. We know that an abundance of algae (Pea Soup) is symptomatic of more basic problems such as overfeeding, overcrowding and accumulation of organic debris, among other things and corrective steps should be taken. On the flip side of the coin, some level of Nitrate SHOULD be detectable. A complete absence of Nitrate indicates water quality issues and could be more problematic than an excessive amount.

 (NOTE: Algaecides are not recommended as their use will very likely result in reduced Oxygen levels while doing nothing to reduce the nutrient level in the water. In fact, as the algae die and decompose, nutrients are released back into the water bringing the process full circle.)

I find it hard to imagine that Carp (Koi), given their native habitat, their preference for muddy, nutrient rich water and their adaptability, would ever have a problem with Nitrate toxicity…. at least in a Garden Pond (eco-system) setting as long as Nitrate levels increased over time and the increase was not large and abrupt.

The true Koi Pond, because of its lack of plants, does present problems with Nitrate levels. Not because it is a health problem (albeit remote) for the fish, but because of the potential need for algae control. A true Koi Pond is constructed specifically for the viewing of its occupants, so water clarity is of prime concern. Excessive Nitrate levels in Koi Ponds are usually controlled by water changes and by the process of Denitrifcation.

This will be the subject of our next post.

Are Koi Wusses? Part VII - Nitrite

 We know that the product of Ammonia oxidation is Nitrite. This is also toxic to Carp (Koi) at very low levels. Any reading greater than 0.06 mg/L is considered lethal. This level is roughly equivalent to one drop in a pint of water.

Like Ammonia, Nitrite toxicity is influenced by both pH and temperature .In one study, two (2) different groups of Carp (Cyprinus carpio) were subjected to nitrite levels of 0.0667 for 48 hours at temperatures of 14C/57F and 20C/68F. The mortality rate for each group was 30% and 51% respectively.

In addition toxic effects of nitrate are more likely at low dissolved Oxygen levels.

Nitrite toxicity occurs as Nitrite enters the fish by way of the gills and passes into the circulatory system (Perrone, 1977). Toxic effects of nitrite include oxidation of hemoglobin to methemoglobin, a form incapable of binding molecular oxygen (Brown and McLey, 1975).

Fish with methemoglobin can be detected by the colour of the blood and also by brown colour of the gills (Brown Blood Disease). As nitrite rises, the fraction of methemoglobin in the blood reduces the oxygen carrying capacity of the blood (Cameron, 1971). Fish with elevated levels of methemoglobin may suffer from anoxia (Tomasso, 1981). . Since methemoglobin does not transport oxygen, asphyxiation is the principal reason fish die from nitrite poisoning

Nitrite is less toxic than Ammonia, but the toxic effects of Nitrite occur much more rapidly than those of  Ammonia.

Chloride is used to “treat’ Nitrite toxicity. This may be Sodium Chloride (Pond Salt) or Calcium Chloride, which is more expensive. The chloride portion of salt competes with nitrite for absorption through the gills .If problems with Nitrite levels exist, maintaining at least a 10 to 1 ratio of chloride to nitrite in a pond effectively prevents nitrite from entering Koi.  As a general rule, 50 to 100 ppm chloride in pond waters will guard against high spikes of nitrite concentration. 1,000 ppm of salt is equal to a 0.1% level. (Note: This should be done only if a Nitrite problem is detected. Maintaining salt levels will over time result in parasites and other pathogenic organisms adapting to these salinity levels making them harder to control through the normal “Salt Treatments” .Use Salt only as a temporary fix. Adequate bio-filtration (bioconversion) will maintain safe nitrite levels.)

It should be noted that Carp(Koi) can survive ‘Brown Blood Disease’ if treated in time, but with a resulting lowered immune system making them more susceptible to other infections that can occur for up to 3 weeks after the “Brown Blood Disease’ is cured.

Carp(Koi), though highly adaptable are as susceptible to Nitrite poisoning and it’s effects as any other fish
Nitrite level is probably the most important water quality parameter because it’s effects occur rapidly and should be tested for frequently along with Ammonia.

Next Post:  Nitrates